Polycyclic aromatic hydrocarbons (PAHs): Updated aspects of their determination, kinetics in the human body, and toxicity.

Polycyclic aromatic hydrocarbons (PAHs) are legacy pollutants of considerable public health concern. Polycyclic aromatic hydrocarbons arise from natural and anthropogenic sources and are ubiquitously present in the environment. Several PAHs are highly toxic to humans with associated carcinogenic and mutagenic properties. Further, more severe harmful effects on human- and environmental health have been attributed to the presence of high molecular weight (HMW) PAHs, that is PAHs with molecular mass greater than 300 Da. However, more research has been conducted using low molecular weight (LMW) PAHs). In addition, no HMW PAHs are on the priority pollutants list of the United States Environmental Protection Agency (US EPA), which is limited to only 16 PAHs. However, limited analytical methodologies for separating and determining HMW PAHs and their potential isomers and lack of readily available commercial standards make research with these compounds challenging. Since most of the PAH kinetic data originate from animal studies, our understanding of the effects of PAHs on humans is still minimal. In addition, current knowledge of toxic effects after exposure to PAHs may be underrepresented since most investigations focused on exposure to a single PAH. Currently, information on PAH mixtures is limited. Thus, this review aims to critically assess the current knowledge of PAH chemical properties, their kinetic disposition, and toxicity to humans. Further, future research needs to improve and provide the missing information and minimize PAH exposure to humans.

Endocrine disrupting chemicals associated with dry eye syndrome.

BACKGROUND: Dry eye syndrome (DES) is a multifactorial disease that causes changes in the tear film and occurs more frequently in women. Sex hormones (SHs) influence tear production, and SHs imbalance is associated with DES. Endocrine-disrupting chemicals (EDCs) are compounds that can bind to SHs receptors, changing the SHs action in several organs and tissues. METHODS: The levels of 21 EDCs were measured in the urine of DES patients and healthy controls. All individuals were submitted to eye exams for DES and responded to the questionnaire "Ocular Surface Disease Index (OSDI)". DES was considered present when the OSDI score was >20 and one of the DES tests surpassed the established thresholds. RESULTS: Methyl-protocatechuic acid (OHMeP), had higher urine levels in DES individuals than in control individuals (p = 0.0189). On the other hand, triclocarban (TCC) exhibited lower urine levels in DES individuals than in control individuals (p = 0.0081). Statistically significant positive associations were found between Methyl Paraben (MeP), EtP (ethyl paraben) and OHMeP with fluorescein staining test; between TCC and Tear breakup time test and between OHMeP and OSDI score. Significant negative associations were found between EtP and OHMeP and schirmer test; between OHMeP and Tear breakup time test; between TCC and the OSDI score and fluorescein and lissamine staining test.The quadratic discriminant function classified 94.4% of individuals in their groups based on the urine levels of EDCs. CONCLUSION: The following EDCs, MeP, EtP, and OHMeP, were associated with signs and symptoms of DES. TCC had a paradoxical protective effect against DES. These findings suggest that EDCs are associated with DES and the exposure should be included in the investigation of causes and risk factors for DES.

The role of endocrine disruptors in ocular surface diseases.

Endocrine disruptors are a group of compounds that occur in increasing amounts in the environment. These compounds change the hormone homeostasis of the target organs regulated by those hormones, mostly by binding to their receptors and affecting their signaling pathways. Among the hormones altered by endocrine disruptors are sex hormones, thyroid hormones, and insulin. Studies have documented abnormalities in the reproductive and metabolic systems of various animal species exposed to endocrine disruptors. Endocrine disruptors can play a significant role in ocular diseases once hormone deficiency or excess are involved in the mechanism of that disease. Cataracts, dry eye disease and retinal diseases, such as macular hole and diabetic retinopathy, are some of the frequent problems where hormones have been implicated. We found that some compounds function as endocrine disruptors in the metabolism of body organs and systems. The increasing frequency of dry eye and other ocular diseases indicates the need to better investigate the potential relationships beyond the isolated associations mentioned by patients and documented as rare case reports. The evidence from case-control studies and experimental assays can provide the information necessary to confirm the endocrine effects of these chemicals in the pathophysiology of dry eye disease. We hypothesize that endocrine disruptors may contribute to the increase of ocular diseases, such as dry eye disease, in recent years.